Splices comprising honeycomb cores supported by tie clips and methods of forming thereof

ABSTRACT

Provided are splices comprising honeycomb cores and adhesive layers with tie clips supporting the honeycomb cores. Also provided are methods of forming such splices. Each tie clip includes two legs and a bridging portion joining the legs. When forming a splice, an adhesive layer is positioned between two honeycomb cores. One leg of the tie clip is inserted into the full cell of one honeycomb core, while the other leg is inserted into the full cell of the other honeycomb core. The bridging portion extends across the adhesive layer. While curing the adhesive layer, the tie clip supports the honeycomb cores with respect to each other and maintains their orientation. The tie clip becomes a part of the splice. The tie clip may be buried in the honeycomb cores without extending above the first face of the splice.

BACKGROUND

Various applications, such as applications requiring large components,often involve splicing honeycomb cores. The resulting spliced assembliesmay be referred to as splices. The need for splicing occurs, forexample, when initial structures have a limited size. Splices may beused for various aircraft applications, such as interior aircraftpanels, padding devices design to absorb impact, and other likeapplications.

Honeycomb cores may be spliced using various adhesive. For example,cells of two honeycomb cores may be aligned, and these structures may bepushed into contact with an adhesive layer disposed between thestructures. When curing this adhesive layer, the gap between the twostructures may change, for example, because of expansion of the adhesivelayer. Supporting the two structures may be challenging especially whenthe adhesive layer and the structures are covered by additionalcomponents, such as face sheets. For example, conventional solutions ofusing external removable supports do not allow integration of the facesheet into the adhesive curing process. The curing has to be performedwithout the face sheet. After the curing, these external supports areremoved, and the face sheet is added and cured in a separate process.Another conventional approach is based on inserting a small piece of ahoneycomb core across the splice interface to bridge the interface.However, this approach does not work well for many types of honeycombcores, such as NOMEX® cores. When the bridging honeycomb piece isinserted over the two honeycomb cores, it shears the walls of these twohoneycomb cores and may cause the overall splice to crush because ofthis wall cutting.

There is a need for new types of splices comprising adhered andsupported honeycomb cores and new methods of forming thereof, inparticular, for sandwiched honeycomb cores.

SUMMARY

Provided are splices comprising honeycomb cores and adhesive layers withtie clips supporting the honeycomb cores. Also provided are methods offorming such splices. Each tie clip includes two legs and a bridgingportion joining the legs. When forming a splice, an adhesive layer ispositioned between two honeycomb cores. One leg of the tie clip isinserted into the full cell of one honeycomb core, while the other legis inserted into the full cell of the other honeycomb core. The bridgingportion extends across the adhesive layer. While curing the adhesivelayer, the tie clip supports the honeycomb cores with respect to eachother and maintains their orientation. The tie clip becomes a part ofthe splice. The tie clip may be buried in the honeycomb cores withoutextending above the first face of the splice.

In some embodiments, a method of adhering two honeycomb cores comprisesapplying an adhesive layer between a first honeycomb core and a secondhoneycomb core, inserting a first plurality of tie clips into the firsthoneycomb core and into the second honeycomb core, and curing theadhesive layer while the first plurality of tie clips is inserted intothe first honeycomb core and the second honeycomb core. When theadhesive layer is applied between the first honeycomb core and thesecond honeycomb core, the adhesive layer directly interfaces the firsthoneycomb core and the second honeycomb core.

In some embodiments, inserting the first plurality of tie clips into thefirst honeycomb core and the second honeycomb core comprises bridging afull cell of the first honeycomb core with a full cell of the secondhoneycomb core. This bridging of the full cell of the first honeycombcore with the full cell of the second honeycomb core may compriseinserting a first leg of each tie clip of the first plurality into afull cell of the first honeycomb core. The bridging may furthercomprises inserting a second leg of each tie clip of the first pluralityinto a full cell of the second honeycomb core.

In some embodiments, curing the adhesive layer comprises maintaining aset distance between the first honeycomb core and the second honeycombcore using the first plurality of tie clips. Curing the adhesive layermay also comprise adhering the first plurality of tie clips to theadhesive layer.

In some embodiments, prior to curing the adhesive layer, the method maycomprise positioning a face sheet over the splice. The face sheet mayinterface the first honeycomb core, the second honeycomb core, theadhesive layer, and the first plurality of tie clips. In someembodiments, the method further comprises forming the face sheet and thefirst plurality of tie clips from a same material, such as a fiberreinforced material or, more specifically, a fiberglass. In someembodiments, the method further comprises forming the first plurality oftie clips from a pre-impregnated composite lamina sheet.

In some embodiments, inserting the first plurality of tie clipscomprises positioning top edges of the first plurality of tie clips at alevel or below a first face of the first honeycomb core and a first facethe second honeycomb core. Specifically, inserting the first pluralityof tie clips may comprise protruding a bridging portion of each tie clipof the first plurality into the adhesive layer, into a wall of the fullcell of the first honeycomb core, and into a wall of the full cell ofthe second honeycomb core. In some embodiments, the method furthercomprises forming the first plurality of tie clips with a height of thebridging portion of each of the first plurality of tie clips being lessthan 10% of a height of the first honeycomb core or of the secondhoneycomb core.

In some embodiments, the method further comprises forming the firstplurality of tie clips with a height of each of the first plurality oftie clips being at least 80% of a height of the first honeycomb core orof the second honeycomb core.

In some embodiments, inserting the first plurality of tie clips into thesplice comprises aligning each tie clip in the first plurality such thatan angle of each of the first plurality of tie clips relative to a firstface of the first honeycomb core and a first face of second honeycombcore is substantially same. Alternatively, inserting the first pluralityof tie clips into the splice comprises aligning each tie clip in thefirst plurality such that angles of tie clips of the first plurality oftie clips relative to the adhesive layer varies.

In some embodiments, the method further comprises forming the firstplurality of tie clips having a first leg, a second leg parallel to thefirst leg, and a bridging portion extending between and connecting thefirst leg and the second leg.

In some embodiments, inserting the first plurality of tie clips into thesplice comprises evenly distributing tie clips in the first plurality oftie clips along a length of the adhesive layer.

In some embodiments, curing the adhesive layer the adhesive layercomprises contacting a wall of a full cell of the first honeycomb corewith a first leg of at least one of the first plurality of tie clips andcontacting a wall of a full cell of the second honeycomb core with asecond leg of the same one of the first plurality of tie clips.

In some embodiments, a first face of the first honeycomb core and afirst face the second honeycomb core are non-planar after curing theadhesive layer.

In some embodiments, the method further comprises inserting a secondplurality of tie clips into the splice. The bridging portions of thefirst plurality may be adjacent to a first face of the first honeycombcore. The bridging portions of the second plurality may be adjacent to asecond face of the first honeycomb core opposite of the first face.

In some embodiments, at least one of the first plurality of tie clipsand one of the second plurality of tie clips protrude into a same fullcell of the first honeycomb core.

In some embodiments, inserting the first plurality of tie clips andinserting the second plurality of tie clips into the splice comprisesinserting one of the first plurality of tie clips but no tie clips ofthe second plurality of tie clips into at least one full cell of thefirst honeycomb core.

In some embodiments, inserting a second plurality of tie clips into thesplice comprises offsetting the second plurality of tie clips relativeto the first plurality of tie clips along the adhesive layer.

In some embodiments, the first honeycomb core and the second honeycombcore form an aircraft structure.

Also provided is a splice comprising: a first core, a second core, anadhesive layer, disposed between and directly interfacing the first coreand the second core, and a first plurality of tie clips inserted intoand bridging the first core to the second core, the first plurality oftie clips being adhered to the adhesive layer.

In some embodiments, each tie clip of the first plurality of tie clipscomprises a first leg, a second leg, and a bridging portion extendingbetween the first leg and the second leg. The first leg of each tie clipis inserted into a full cell of the first honeycomb core. The second legof each tie clip is inserted into a full cell of the second honeycombcore. The bridging portion extends across the adhesive layer,

In some embodiments, the first core is a first honeycomb core, andwherein the second core is a second honeycomb core.

In some embodiments, the splice further comprises a face sheetpositioned over the splice such that the face sheet interfaces the firsthoneycomb core, the second honeycomb core, the adhesive layer, and thefirst plurality of tie clips. The face sheet is bonded to the splice bythe adhesive layer. Top edges of the first plurality of tie clips may beat a level or below the first face of the first honeycomb core and thefirst face the second honeycomb core. In some embodiments, the facesheet and the first plurality of tie clips are made from a samematerial, such as fiberglass.

In some embodiments, a bridging portion of each of the first pluralityof tie clips protrudes into the adhesive layer, into a wall of the fullcell of the first honeycomb core, and into a wall of the full cell ofthe second honeycomb core. The height of the bridging portion of each ofthe first plurality of tie clips may be less than 10% of a height of thefirst honeycomb core or of the second honeycomb core.

In some embodiments, the height of each of the first plurality of tieclips is at least 80% of a height of the first honeycomb core or of thesecond honeycomb core. The angle of each of the first plurality of tieclips relative to the first face of the first honeycomb core and thefirst face of second honeycomb core may be substantially same. In someembodiments, the angles of tie clips of the first plurality of tie clipsrelative to the adhesive layer varies. The first plurality of tie clipsis made from a pre-impregnated composite lamina sheet.

In some embodiments, tie clips in the first plurality of tie clips areevenly distributed along a length of the adhesive layer. Spacing betweeneach pair of adjacent tie clips in the first plurality of tie clips maybe between about 1 inch and 5 inches.

In some embodiments, the adhesive layer is in contact with a wall of thefull cell of the first honeycomb core. and wherein the second leg of thesame one of the first plurality of tie clips is in contact with a wallof the full cell of the second honeycomb core.

In some embodiments, the splice is non-planar after curing the adhesivelayer.

In some embodiments, the splice further comprises a second plurality oftie clips inserted into the splice on a side of the splice opposite ofthe first plurality of tie clips. At least one of the first plurality oftie clips and one of the second plurality of tie clips may protrude intoa same full cell of the first honeycomb core. At least one full cell ofthe first honeycomb core may receive one of the first plurality of tieclips but no tie clips of the second plurality of tie clips. The firstplurality of tie clips may be offset relative to the second plurality oftie clips along the adhesive layer.

These and other embodiments are described further below, with referenceto the figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a process flowchart of a method of adhering two honeycombcores, in accordance with some embodiments.

FIG. 2A is a schematic top view of two honeycomb cores prior to adheringthese cores, in accordance with some embodiments.

FIG. 2B is a schematic top view of two honeycomb cores with an adhesivelayer disposed between and interfacing these honeycomb cores, inaccordance with some embodiments.

FIG. 2C is a schematic top view of a splice including two honeycombcores with an adhesive layer disposed between and interfacing thesehoneycomb cores and a plurality of tie clips inserted into full cells ofthese honeycomb cores, in accordance with some embodiments.

FIG. 2D is a schematic cross-sectional side view of the splice of FIG.2A illustrating position of a tie clips within the splice, in accordancewith some embodiments.

FIG. 2E is a schematic cross-sectional side view of another example ofthe splice of FIG. 2A, in accordance with some embodiments.

FIG. 2F is a schematic cross-sectional side view of the splice of FIG.2E illustrating the bridging portion of the tie clip protruding into thewall of the full cell of the first honeycomb core, in accordance withsome embodiments.

FIG. 2G is a schematic cross-sectional side view of the splice of FIG.2E illustrating the bridging portion of the tie clip protruding into theadhesive layer, in accordance with some embodiments.

FIG. 2H is a schematic cross-sectional side view of the splice of FIG.2E illustrating the bridging portion of the tie clip protruding into thewall of the full cell of the second honeycomb core, in accordance withsome embodiments.

FIG. 2I is a schematic cross-sectional side view of another example ofthe splice, in accordance with some embodiments.

FIG. 3 is a schematic top view of a splice showing distributing of tieclips along the adhesive layer, in accordance with some embodiments.

FIG. 4 is a schematic cross-sectional side view of a non-planar splice,in accordance with some embodiments.

FIG. 5A is a schematic cross-sectional side view of a splice having twopluralities of tie clips inserted from opposite sides of the honeycombcores, in accordance with some embodiments.

FIG. 5B is a schematic top view of the splice of FIG. 5A showingorientation of the two pluralities of tie clips, in accordance with someembodiments.

FIG. 5C is a schematic top view of the splice of FIG. 5A showing anotherexample of orientation of the two pluralities of tie clips, inaccordance with some embodiments.

FIGS. 6A-6E are photographs of actual test splices at variousfabrication stages.

FIG. 7 is a block diagram of aircraft production and service methodologythat may utilize methods and systems for adhering honeycomb coresdescribed herein.

FIG. 8 is a schematic illustration of an aircraft that may includesplices formed by adhering honeycomb cores described herein.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth inorder to provide a thorough understanding of the presented concepts. Thepresented concepts may be practiced without some or all of thesespecific details. In other instances, well known process operations havenot been described in detail so as to not unnecessarily obscure thedescribed concepts. While some concepts will be described in conjunctionwith the specific embodiments, it will be understood that theseembodiments are not intended to be limiting.

Introduction

When two honeycomb cores are bonded together used an adhesive layer(e.g., adhesive foam), the adhesive layer may expand during its curingand push the cores apart. As a result, the assembly (splice) formed bybonding the two honeycomb cores with the adhesive layer needs to beinspected and, in some instances, discarded. Furthermore, for visualinspection, the initial assembly must be cured separate from a facesheet in order to see the adhesive layer after curing. Otherwise, whenthe face sheet is cured together with the adhesive layer, the inspectionhas to be performed using complex and expensive techniques (e.g.,X-Ray).

Spliced honeycomb assemblies or simply splices described herein areformed with no or minimal impact to the walls of the honeycomb coreswhile maintaining a set gap between spliced honeycomb cores. A spliceincludes tie clips supporting the honeycomb cores while curing theadhesive layers and preventing excessive expansion of the adhesivelayer. Specifically, each tie clip includes two legs and a bridgingportion extending between and joining the legs. One leg of this tie clipis inserted into a full cell of one honeycomb core, while the other legis inserted into a full cell of the other honeycomb core. The full cellsreceiving different legs of the same tie clip may be adjacent full cellsof the two honeycomb cores. The bridging portion extends across anadhesive layer and collectively with the legs maintain orientation ofthe full cells with respect to each other. Multiple tie clips may beinserted along the adhesive layer and collectively these clips maintainorientation of the two honeycomb cores. While the bridging portion maycome in contact with the adhesive layer, the legs may be disposed in thefull cells of the honeycomb cores that are substantially free from theadhesive. Limiting the adhesive to fewer cells of the honeycomb coresmay be used to keep down the weight of the overall assembly.

While curing the adhesive layer, the tie clips support the honeycombcores with respect to each other and prevent their separation due to,for example, expansion of the adhesive layer. After curing, the tie clipremains in the splice and may be also bonded to the adhesive layer. Insome embodiments, the face sheet may be adhered to the slice assemblywhile curing of the adhesive layer. This approach of using embedded tieclips allows to expedite processing. For example, the splice may becured together with the face sheet and the embedded tie clips under theface sheet. Furthermore, adding embedded tie clips eliminates the needfor complex post cure inspections (e.g., X-Ray) since the embedded tieclips maintain registration of the two honeycomb cores relative to eachother.

Examples of Splices and Methods of Forming Such Splices

FIG. 1 is a process flowchart of method 100 of adhering two honeycombcores 210 and 220, in accordance with some embodiments. Two honeycombcores 210 and 220 are shown in FIG. 2A prior to executing method 100.Method 100 comprise operation 110, which involves applying adhesivelayer 230 between first honeycomb core 210 and second honeycomb core220. Splice 200 shown in FIG. 2B is formed during this operation.Adhesive layer 230 is not yet cured at this stage.

FIG. 2A is a schematic top view of first honeycomb core 210 and secondhoneycomb core 220 prior to operation 110, while FIG. 2B is a similarschematic top view of partially formed splice 200 after completingoperation 110. Splice 200 comprises first honeycomb core 210, secondhoneycomb core 220, and adhesive layer 230 disposed (e.g., sandwiched)between and interfacing first honeycomb core 210 and second honeycombcore 220. Splice does not include tie clips 250 at this stage.

First honeycomb core 210 includes full cells 212. Unlike partial cells214, full cells 212 have a complete periphery with all walls intact.Full cells 212 are later used for receiving tie clips 250. Firsthoneycomb core 210 may also include partial cells 214, which haveportions of walls removed and incomplete peripheries. When present,partial cells 214 are not be used for insertion of tie clips 250. Unlikefull cells 212, partial cells 214 may not be able to restrict legs oftie clips 250 in directions parallel to first face 215 of firsthoneycomb core 210.

In a similar manner, second honeycomb core 220 includes full cells 222,which have all walls intact. Full cells 222 are later used for insertionof tie clips 250. Second honeycomb core 220 may also include partialcells 224, which have portions of walls removed, and which will not beused for insertion of tie clips 250.

In some embodiments, first honeycomb core 210 is aligned relative tosecond honeycomb core 220 along adhesive layer 230 (the Y direction inFIG. 2B). For example, wall edges 211 of partial cells 214 may coincidewith wall edges 221 of partial cells 224 as, for example, shown in FIG.2B. In some embodiments, wall edges 211 of partial cells 214 may beoffset relative wall edges 221 of partial cells 224 along adhesive layer230.

When partial cells 214 and partial cells 224 are present, adhesive layer230 may partially penetrate in these partial cells while forming splice200 as, for example, shown in FIG. 2B and, in some embodiments, laterwhile curing adhesive layer 230 as, for example, shown in FIG. 2C. Thisadhesive penetration feature provides a larger interface area betweenadhesive layer 230 and first honeycomb core 210 and between adhesivelayer 230 and second honeycomb core 220. Furthermore, this feature(adhesive expanding into partial cells 214 and 224) provides space foradhesive layer 230 to expand into during its curing while maintainingthe same spacing between first honeycomb core 210 and second honeycombcore 220.

Method 100 may involve forming first plurality 240 of tie clips 250during operation 119. For example, first plurality 240 of tie clips 250may be formed with height 264 of bridging portion 253 of each of firstplurality 240 of tie clips 250 being less than 10% of a height 260 offirst honeycomb core 210 or of second honeycomb core 220. In someembodiments, first plurality 240 of tie clips 250 may be formed withheight 262 of each of first plurality 240 of tie clips 250 being atleast 80% of a height 260 of first honeycomb core 210 or of secondhoneycomb core 220. First plurality 240 of tie clips 250 may be formedfrom a pre-impregnated composite lamina sheet. In some embodiments,first plurality 240 of tie clips 250 are formed having a first leg 251,a second leg 252 parallel to first leg 251, and a bridging portion 253extending between and connecting first leg 251 and second leg 252.

Method 100 may proceed with inserting first plurality 240 of tie clips250 into splice 200 or, more specifically into first honeycomb core 210and into second honeycomb core 220 during operation 120 (referring toFIG. 1). FIGS. 2C-2E and FIG. 3 illustrate different views and examplesof splice 200 after completing operation 120. Referring to FIG. 2D, eachtie clip 250 comprises first leg 251, second leg 252, and bridgingportion 253, which extends between and joins first leg 251 and secondleg 252. For purposes of this disclosure, first leg 251 and second leg252 are defined as portions of tie clip 250 that extend the entireheight 262 of tie clip 250. Height 264 of bridging portion 253 is lessthan the entire height 262 of tie clip 250. Depending on the design oftie clip 250, height 264 of bridging portion 253 may be variable as itextends between first leg 251 and second leg 252 (the X direction inFIG. 2D). Each of first plurality 240 of tie clips 250 may have aU-shape. Height 262 of tie clips 250 may at least 60% of height 260 offirst honeycomb core 210 or of second honeycomb core 220 as shown inFIG. 2E or, more specifically, at least about 70% or even at least about80% or at least about 90%.

During operation 120, first leg 251 of tie clip 250 is inserted intofull cell 212 of first honeycomb core 210 as shown in FIGS. 2D and 2E.Likewise, second leg 252 of tie clip 250 is inserted into full cell 222of second honeycomb core 220. Bridging portion 253 extends acrossadhesive layer 230. Referring to FIG. 2F, angle 267 of each tie clips250 relative to first face 215 of first honeycomb core 210 and firstface 225 of second honeycomb core 220 may be substantially same.Specifically, this angle 267 may be about 90°. Referring to FIG. 2C,angles 269 of tie clips 250 relative to adhesive layer 230 may vary.Some clips (e.g., tie clip 250 b in FIG. 2C) may be at an angle of about90° relative to adhesive layer 230. However, tie clip 250 a in FIG. 2Chas a different angle. Angle 269 may depend on orientation of the twofull cells which receive the legs of tie clip 250 a. Angle 269 may alsodepend on the size and shape of the full cells relative to the size andshape of the legs and ability of the legs to turn and move with the legsduring insertion and later. The difference in angle 269 may be due torelative positions of full cells 212 and 222 along adhesive layer aswell as sizes of full cells 212 and 222 and legs 251 and 262.Furthermore, bridging portions 253 with different lengths may be used insome embodiments.

In some embodiments, first plurality 240 of tie clips 250 is made from apre-impregnated composite lamina sheet, (e.g., fiber reinforced tieclips 250). Selection of materials for tie clips 250 may depend onmaterials of first honeycomb core 210, second honeycomb core 220,adhesive layer 230, and/or face sheet 270 (if one is used). For example,the material of tie clips 250 may have a coefficient of thermalexpansion (CTE) that is within 50% or even within 25% of CTEs of othercomponents around tie clips 250.

Referring to FIG. 3, tie clips 250 may be evenly distributed alonglength 231 of adhesive layer 230. For example, spacing 268 between eachpair of adjacent tie clips 250 may vary by less than 50% from averagespacing 268 or even less than 25% or even less than 10%. Average spacing268 between each pair of adjacent tie clips 250 in first plurality 240may be between about 1 inch and 5 inches or, more specifically, betweenabout 2 inches and 4 inches. The spacing may be determined based onsupport needed for honeycomb cores 210 and 220. Furthermore, the spacingmay be determined based on characteristics of adhesive layer 230.Additional factors include the cell height, the wall thickness of thecell, adhesive properties (e.g., material, thickness, coefficient ofthermal expansion), assembly requirements. In some embodiments, tieclips 250 can be used to maintain registration of first honeycomb core210 and second honeycomb core 220 that are non-planar (e.g., countered)either while forming (e.g., curing) splice 200 or at later operations.One example of such non-planar splice 200 is shown in FIG. 4 anddescribed below with reference to this figure.

After tie clips 250 are inserted into splice 200, a portion of tie clips250 may extend above first face 215 of first honeycomb core 210 and alsoabove first face 225 of second honeycomb core 220 as, for example, shownin FIG. 2D. In this example, bridging portion 253 may extend over walls213 of first honeycomb core 210 and walls 223 of second honeycomb core220 and not cut into these walls 213 and 223. Furthermore, bridgingportion 253 may extend over adhesive layer 230 rather than cutting intoadhesive layer 230. This example may be used when extending tie clipsabove first faces 215 and 225 is acceptable and/or when cutting intothese walls 213 and 223 should be avoided. Bridging portion 253 may havesmall height 264 in these examples.

Alternatively, the top edge of tie clips 250 may be at the same levelwith first faces 215 and 225 as, for example, shown in FIG. 2E. In thisexample, top edges 254 of tie clips 250 are at the level (as shown inFIG. 2E) or below first face 215 of first honeycomb core 210 and firstface 225 second honeycomb core 220. In this example, while insertingfirst plurality 240 of tie clips 250 into splice 200, bridging portion253 may protrude into adhesive layer 230, into wall 213 of full cell 212of first honeycomb core 210, and into wall 223 of full cell 222 ofsecond honeycomb core 220. Height 264 (e.g., average height 264, if thisheight is variable) of bridging portion 253 of tie clips 250 may be lessthan 10% of height 260 of first honeycomb core 210 or of secondhoneycomb core 220 or even less than 5%. As such, distortions to walls213 and 223 are minimal. This example may be used when planar first face201 of splice 200 is needed. For example, first face 201 may receiveface sheet 270 at a later operation. It should be noted that at leastportions of first faces 215 and 225 adjacent to adhesive layer 230 maybe coplanar.

As such, operation 120 (inserting first plurality 240 of tie clips 250into first honeycomb core 210 and second honeycomb core 220) maycomprise bridging full cell 212 of first honeycomb core 210 with fullcell 222 of second honeycomb core 220, which is reflected assub-operation 122 in FIG. 1. This bridging sub-operation 122 maycomprise inserting first leg 251 of each tie clip 250 of first plurality240 into full cell 212 of first honeycomb core 210 (sub-operation 123)and may further comprises inserting 120 second leg 252 of each tie clip250 of first plurality into full cell 222 of second honeycomb core 220(sub-operation 124).

In some embodiments, inserting first plurality 240 of tie clips 250during operation 120 comprises positioning top edges 254 of firstplurality 240 of tie clips 250 at a level or below a first face 215 offirst honeycomb core 210 and a first face 225 second honeycomb core 220as reflected by sub-operation 125 in FIG. 1. Furthermore, insertingoperation 120 may comprise protruding bridging portion 253 of each tieclip of first plurality 240 into adhesive layer 230, into wall 213 offull cell 212 of first honeycomb core 210, and into wall 223 of fullcell 222 of second honeycomb core 220 as reflected by sub-operation 126in FIG. 1.

In some embodiments, inserting 120 first plurality 240 of tie clips 250comprises aligning each tie clip 250 in first plurality such that anangle 267 of each of first plurality 240 of tie clips 250 relative to afirst face 215 of first honeycomb core 210 and a first face 225 ofsecond honeycomb core 220 is substantially same, as reflected bysub-operation 127 in FIG. 1. Sub-operation 127 may involve aligning eachtie clip 250 in first plurality such that angles 269 of tie clips 250 offirst plurality 240 of tie clips 250 relative to adhesive layer 230varies. Inserting operation 120 may also comprise evenly distributingtie clips 250 in first plurality 240 of tie clips 250 along a length 231of adhesive layer 230 as reflected by sub-operation 128 in FIG. 1.

In some embodiments, method 100 also involves inserting second plurality280 of tie clips 250 into splice 200 during optional operation 130(referring to FIG. 1). As shown in FIG. 5A, second plurality 280 isinserted on side 201 of splice 200 opposite of first plurality 240. Tieclips 250 in first plurality 240 may be the same or different as tieclips 250 in second plurality 280.

Tie clips 250 of first plurality 240 and second plurality 280 may beinserted into the same or different full cells of honeycomb cores 210and 220. Referring to FIG. 5B, tie clip 250 a of first plurality 240 andtie clip 250 b of second plurality 280 protrude into same full cell 212of first honeycomb core 210. The same tie clips 250 a and 250 b alsoprotrude into same full cell 222 of second honeycomb core 210. Tie clips250 a and 250 b may or may not overlap in these cells along structures'height 260. Referring to the example illustrated in FIG. 5A where tieclips 250 a and 250 b do not overlap, a combination of tie heights 262 sand 262 b may be less than structure height 260. Alternatively, tieclips 250 of first plurality 240 may overlap with tie clips 250 ofsecond plurality 280 in the same cells. Specifically, a combination oftie height 262 a and tie height 262 b may be greater that structureheight 260. In some embodiments, each of tie height 262 a and tie height262 b may greater than the half of structure height 260.

Referring to FIG. 5C, in some embodiments, at least one full cell 212 aof first honeycomb core 210 receives one tie clip 250 a of firstplurality 240 but no tie clips of second plurality 280 of tie clips.Specifically, tie clip 250 a is inserted into full cell 212 a and fullcell 222 a. Neither one of tie clips 250 b and 250 d of second plurality280 is inserted into either full cell 212 a and full cell 222 a. In asimilar manner, tie clip 250 b of second plurality 280 is inserted intofull cell 212 b and full cell 222 b. Neither one of tie clips 250 a, 250c, and 250 e of first plurality 240 is inserted into either full cell212 b and full cell 222 b. In this example, first plurality 240 of tieclips is offset relative to second plurality 280 of tie clips alongadhesive layer 230.

In some embodiments, method 100 also involves positioning face sheet 270over splice 200 during optional operation 140 (refer to FIG. 1).Operation 140 is performed prior to curing adhesive layer 230. As such,when adhesive layer 230 is later cured, face sheet 270 is also bonded tosplice 200.

An example of splice 200 with face sheet 270 positioned over it ispresented in FIG. 2I. In this example, face sheet 270 interfaces firsthoneycomb core 210 and second honeycomb core 220. Face sheet 270 mayalso interface with adhesive layer 230, which may at least in partsupport face sheet 270. Furthermore, face sheet 270 may also interfacefirst plurality 240 of tie clips 250. Face sheet 270 is adhered tosplice 200 after curing adhesive layer 230, which is further describedbelow. In some embodiments, face sheet 270 and first plurality 240 oftie clips 250 are both made from the same material. For example, facesheet 270 and first plurality 240 of tie clips 250 may be both made fromfiberglass. Furthermore, face sheet 270 can be also bonded to tie clips250. As shown in FIG. 2I, the assembly may include two face sheets 270and 271 with splice 200 disposed (sandwiched) in between face sheets 270and 271.

In some embodiments, method 100 further comprising forming face sheet270 during optional operation 139. Face sheet 270 and first plurality240 of tie clips 250 may be formed from the same material, such as afiber reinforced material or, more specifically, a fiberglass.

Method 100 may proceed with curing (operation 150) adhesive layer 230while first plurality 240 of tie clips 250 is inserted into splice 200.For example, splice 200 may be heated (sub-operation 152) and/orpressurized (sub-operation 154). Furthermore, splice 200 may be shaped(sub-operation 156). One example of shaped splice 200 is shown in FIG.4. During this collective operation 150, first plurality 240 of tieclips 250 maintains set distance 266 (shown in FIG. 2C) between firsthoneycomb core 210 and second honeycomb core 220. As such, curingadhesive layer 230 may comprise maintaining this set distance 266between first honeycomb core 210 and second honeycomb core 220 usingfirst plurality 240 of tie clips 250, as reflected by operation 160 inFIG. 1. Furthermore, curing adhesive layer 230 comprises adhering firstplurality 240 of tie clips 250 to adhesive layer 230, as reflected byoperation 162 in FIG. 1.

In some embodiments, adhesive layer 230 expands during curing operation150. This expansion may cause first leg 251 of tie clip 250 to come incontact with wall 213 of full cell 212 as, for example, shown in FIG.2D. Furthermore, this expansion may cause second leg 252 of same tieclip 250 of first plurality 240 to come in contact with wall 223 of fullcell 222, which is also shown in FIG. 2D. After contacting walls 213 and223, tie clip 250 will prevent further separation of honeycomb cores 210and 220. Adhesive layer 230 may continue to expand without changing therelative position of honeycomb cores 210 and 220. For example, adhesivelayer 230 may be expanded into open cells of honeycomb cores 210 and220. In other words, tie clips 250 hold honeycomb cores 210 and 220together in proper relationship during adhesive layer 230 curing. Insome embodiments, legs 251 and 252 of tie clip 250 may be equal to thewidth (in the X direction) of full cells 212 and 222 such that tie clip250 is in contact with wall 213 of full cell 212 and wall 223 of fullcell 222 at the time of the insertion of tie clip 250. As such, tie clip250 may prevent expansion of adhesive layer 230 right from start.Furthermore, tie clip 250 may prevent for honeycomb cores 210 and 220from getting closer to each other (e.g., if adhesive layer 230 shrinks).

After completing curing operation 150, first plurality 240 of tie clips250 is adhered to adhesive layer 230 and integrated into splice 200. Inother words, first plurality 240 of tie clips 250 cannot be removed fromsplice 200. In some embodiments, splice 200 may be buried under othercomponents, such as face sheet 270, which may be also bonded to splice200 during cure operation 150.

As such, curing adhesive layer 230 may comprise contacting wall 213 offull cell 212 of first honeycomb core 210 with first leg 251 of at leastone of first plurality 240 of tie clips 250 and contacting wall 223 offull cell 222 of second honeycomb core 220 with second leg 252 of sameone of first plurality 240 of tie clips 250, as reflected by optionaloperation 164 in FIG. 1.

Also provided is splice 200. Slice 200 may comprise first honeycomb core210, second honeycomb core 220, adhesive layer 230, and first plurality240 of tie clips 250. Different views and examples of such splice 200are presented in FIGS. 2C-2I. Adhesive layer 230 is disposed between anddirectly interfaces first honeycomb core 210 and second honeycomb core220. First plurality 240 of tie clips 250 is inserted into splice 200.Specifically, each tie clip 250 of first plurality 240 of tie clips 250comprises first leg 251, second leg 252, and bridging portion 253extending between first leg 251 and second leg 252. First leg 251 ofeach tie clip 250 is inserted into full cell 212 of first honeycomb core210. Second leg 252 of each tie clip 250 is inserted into full cell 222of second honeycomb core 220. Bridging portion 253 extends acrossadhesive layer 230. First plurality 240 of tie clips 250 is adhered toadhesive layer 230 and integrated into splice 200 after curing adhesivelayer 230. Other aspects of splice 200 are presented above withreference to method 100 of forming splice 200.

FIGS. 6A-6E are photographs of actual test splices at variousfabrication stages. Specifically, FIG. 6A illustrates two honeycombcores with an adhesive layer disposed between the structures and tieclips inserted into full cells of these structures. FIG. 6B is aclose-up photo of a similar sample. FIG. 6C is a top down photo of yetanother similar sample. In these examples, the tie clips extend abovethe first faces of the honeycomb cores. The tie clips may be furtherpressed into these structures and adhesive layer to ensure that thefirst face of the overall assembly is flat. FIGS. 6D and 6E are photosof test splices with face sheets positioned over honeycomb cores and tiesplices. In fact, a few tie splices are visible through the face sheetin FIG. 6D. The example presented in FIG. 6E has a flat surface.

Examples of Aircraft and Methods of Fabricating and Operation Aircraft

Examples of the present disclosure may be described in the context ofaircraft manufacturing and service method 1100 as shown in FIG. 8 andaircraft 1102 as shown in FIG. 9. During pre-production, illustrativemethod 1100 may include specification and design (block 1104) ofaircraft 1102 and material procurement (block 1106). During production,component and subassembly manufacturing (block 1108) and inspectionsystem integration (block 1110) of aircraft 1102 may take place.Thereafter, aircraft 1102 may go through certification and delivery(block 1112) to be placed in service (block 1114). While in service,aircraft 1102 may be scheduled for routine maintenance and service(block 1116). Routine maintenance and service may include modification,reconfiguration, refurbishment, etc. of one or more inspection systemsof aircraft 1102. Methods of forming splices comprising honeycomb coresand adhesive layers with tie clips supporting the honeycomb cores may beperformed during one or more of these stages, such as operations 1106,1108, and 1116.

Each of the processes of illustrative method 1100 may be performed orcarried out by an inspection system integrator, a third party, and/or anoperator (e.g., a customer). For the purposes of this description, aninspection system integrator may include, without limitation, any numberof aircraft manufacturers and major-inspection system subcontractors; athird party may include, without limitation, any number of vendors,subcontractors, and suppliers; and an operator may be an airline,leasing company, military entity, service organization, and so on. Thedescribed methods and systems be used on during specification and design(block 1104) of aircraft 1102 and component and subassemblymanufacturing (block 1108). For example, various composite structuresused for airframe and interior may be splices comprising honeycomb coresand adhesive layers with tie clips supporting the honeycomb cores.

As shown in FIG. 9, aircraft 1102 produced by illustrative method 1100may include airframe 1118 with a plurality of high-level inspectionsystems 1120 and interior 1122, which may include the one or more flushmountable bottle openers. Examples of high-level inspection systems 1120include one or more of propulsion inspection system 1124, electricalinspection system 1126, hydraulic inspection system 1128, andenvironmental inspection system 1130. Any number of other inspectionsystems may be included. Although an aerospace example is shown, theprinciples disclosed herein may be applied to other industries, such asthe automotive industry. Accordingly, in addition to aircraft 1102, theprinciples disclosed herein may apply to other vehicles, e.g., landvehicles, marine vehicles, space vehicles, etc.

Apparatus(es) and method(s) shown or described herein may be employedduring any one or more of the stages of manufacturing and service method(illustrative method 1100). For example, components or subassembliescorresponding to component and subassembly manufacturing (block 1108)may be fabricated or manufactured in a manner similar to components orsubassemblies produced while aircraft 1102 is in service (block 1114).Also, one or more examples of the apparatus(es), method(s), orcombination thereof may be utilized during production stages (bock 1108)and (block 1110), for example, by substantially expediting assembly ofor reducing the cost of aircraft 1102. Similarly, one or more examplesof the apparatus or method realizations, or a combination thereof, maybe utilized, for example and without limitation, while aircraft 1102 isin service (block 1114) and/or during maintenance and service (block1116).

Conclusion

Different examples of the apparatus(es) and method(s) disclosed hereininclude a variety of components, features, and functionalities. Itshould be understood that the various examples of the apparatus(es) andmethod(s) disclosed herein may include any of the components, features,and functionalities of any of the other examples of the apparatus(es)and method(s) disclosed herein in any combination, and all of suchpossibilities are intended to be within the spirit and scope of thepresent disclosure.

Many modifications of examples set forth herein will come to mind to oneskilled in the art to which the present disclosure pertains having thebenefit of the teachings presented in the foregoing descriptions and theassociated drawings.

Therefore, it is to be understood that the present disclosure is not tobe limited to the specific examples illustrated and that modificationsand other examples are intended to be included within the scope of theappended claims. Moreover, although the foregoing description and theassociated drawings describe examples of the present disclosure in thecontext of certain illustrative combinations of elements and/orfunctions, it should be appreciated that different combinations ofelements and/or functions may be provided by alternative implementationswithout departing from the scope of the appended claims. Accordingly,parenthetical reference numerals in the appended claims are presentedfor illustrative purposes only and are not intended to limit the scopeof the claimed subject matter to the specific examples provided in thepresent disclosure.

What is claimed is:
 1. A method of joining two honeycomb cores, themethod comprising: inserting a first leg of a tie clip of a firstplurality of tie clips into a full cell of a first honeycomb core and asecond leg of the tie clip into a full cell of a second honeycomb corewhile bridging the first honeycomb core and the second honeycomb corewith a bridging portion of the tie clip, extending between andconnecting the first leg and the second leg; and inserting the bridgingportion into the first honeycomb core and the second honeycomb core,until a top edge of the bridging portion, opposite to free ends of thefirst leg and the second leg, is at a level of a first face of the firsthoneycomb core and a first face of the second honeycomb core.
 2. Themethod of claim 1, wherein inserting the bridging portion comprisesprotruding the bridging portion of the tie clip of the first pluralityof tie clips into a wall of the full cell of the first honeycomb core,and into a wall of the full cell of the second honeycomb core.
 3. Themethod of claim 1, further comprising forming the first plurality of tieclips with a height of the bridging portion of the tie clip of the firstplurality of tie clips being less than 10% of a height of the firsthoneycomb core or a height of the second honeycomb core.
 4. The methodof claim 1, further comprising forming the first plurality of tie clipswith a height of the tie clip of the first plurality of tie clips beingat least 80% of a height of the first honeycomb core or a height of thesecond honeycomb core.
 5. The method of claim 1, further comprisingforming the first plurality of tie clips from a pre-impregnatedcomposite lamina sheet.
 6. The method of claim 1, wherein inserting thefirst leg and the second leg of the tie clip of the first plurality oftie clips comprises evenly distributing tie clips in the first pluralityof tie clips along a length of an interface between the first honeycombcore and the second honeycomb core.
 7. The method of claim 1, whereinthe first face of the first honeycomb core and the first face of thesecond honeycomb core are non-planar.
 8. The method of claim 1, furthercomprising inserting a second plurality of tie clips into the firsthoneycomb core and the second honeycomb core, wherein bridging portionsof the first plurality of tie clips are adjacent to a first face of thefirst honeycomb core, and wherein bridging portions of the secondplurality of tie clips are adjacent to a second face of the firsthoneycomb core opposite of the first face.
 9. The method of claim 1,wherein the first honeycomb core and the second honeycomb core form anaircraft structure.
 10. The method of claim 1, further comprising:applying an adhesive layer between a first honeycomb core and the secondhoneycomb core, the adhesive layer directly interfacing the firsthoneycomb core and the second honeycomb core; and curing the adhesivelayer while the first plurality of tie clips is inserted into the firsthoneycomb core and the second honeycomb core.
 11. The method of claim10, further comprising, prior to curing the adhesive layer, positioninga face sheet over and interfacing the first honeycomb core, the secondhoneycomb core, the adhesive layer, and the first plurality of tieclips.
 12. The method of claim 11, further comprising forming the facesheet and the first plurality of tie clips from a same material.
 13. Themethod of claim 11, further comprising forming the face sheet and thefirst plurality of tie clips are both made from one of a fiberreinforced material or a fiberglass.
 14. The method of claim 10, whereincuring the adhesive layer comprises adhering the first plurality of tieclips to the adhesive layer.
 15. A method of joining two honeycombcores, the method comprising: inserting a first plurality of tie clipsinto a first honeycomb core and into a second honeycomb core; andinserting a second plurality of tie clips into the first honeycomb coreand the second honeycomb core, wherein bridging portions of the firstplurality of tie clips are adjacent to a first face of the firsthoneycomb core, and wherein bridging portions of the second plurality oftie clips are adjacent to a second face of the first honeycomb coreopposite of the first face.
 16. The method of claim 15, wherein at leastone of the first plurality of tie clips and one of the second pluralityof tie clips protrude into a full cell of the first honeycomb core. 17.The method of claim 15, wherein inserting the first plurality of tieclips and inserting the second plurality of tie clips comprisesinserting one of the first plurality of tie clips but no tie clips ofthe second plurality of tie clips into a full cell of the firsthoneycomb core.
 18. The method of claim 15, wherein inserting a secondplurality of tie clips comprises offsetting the second plurality of tieclips relative to the first plurality of tie clips along an interfacebetween the first honeycomb core and the second honeycomb core.
 19. Themethod of claim 15, further comprising: applying an adhesive layerbetween a first honeycomb core and the second honeycomb core, theadhesive layer directly interfacing the first honeycomb core and thesecond honeycomb core; and curing the adhesive layer while the firstplurality of tie clips is inserted into the first honeycomb core and thesecond honeycomb core.
 20. The method of claim 15, wherein top edges ofthe bridging portions of the first plurality of tie clips protrude abovethe first face of the first honeycomb core.